Half of the genome of human herpesvirus 7 (HHV-7) has been cloned. The clones obtained have been mapped after comparison with the sequence of the genome of HHV-6 and human cytomegalovirus. Total or partial sequences have been obtained for the putative glycoprotein H, glycoprotein B, major capsid protein, alkaline exonuclease and phosphotransferase HHV-7 proteins. A bacterial cell wall sulfated polysaccharide~peptidoglycan~ identified as being effective in vitro against Kaposi's sarcoma (KS)-derived cells, is now entering phase one trials at the University of Southern California. Apolipoprotein has been found to be effective in vitro against KS cells and also in a murine KS model. A KS cell line (KS Y-1) has been developed which forms metastatic lethal tumors in immunosuppressed mice. Human beta chorionic gonadotropin, a pregnancy hormone, blocks tumorigenesis and metastasis of neoplastic KS in immunodeficient mice. The percentage of spindle cells in peripheral blood mononuclear cell cultures has been shown to correlate well with the risk for human immunodeficiency virus type 1-infected individuals to develop KS. Immunodeficient mice inoculated with CDI(+) Sup-T1 cells infected with human T-cell leukemia/lymphotropic virus type I (HTLV-I) derived from spontaneous T-cell colonies from patients with HTLV-I-associated neurological (tropical spastic paraparesis/HTLV~I-associated myelopathy) disease or with conditioned medium of those cells develop a neurological pathology similar to that in human patients. No HTLV-I has been recovered from the injected mice. These results show that a neurotoxic molecule which produces the hallmarks of HTLV-I neurological disease is released by some HTLV-I-infected cells. The characterization of this neurotoxic molecule might help elucidate the pathogenic mechanism of HTLV-I-associated neurotoxicity and may also be useful in the understanding of related neurological